Born Joe Yule Jr in New York City, the child of itinerant vaudevillians, Rooney is a legend and a phenomenon. He made his first public appearance aged 17 months as part of the family's stage act and has spent the subsequent 88 years singing, dancing and acting somewhere in the English-speaking world, most recently as Baron Hardup in a 2009 Christmas pantomime in Milton Keynes. His parents parted when he was four and his mother took him to Los Angeles in 1925. Within weeks, he was making one- and two-reel comedies as Mickey McGuire, a name he adopted by deed poll before switching in the early 1930s to Rooney (an improvement on his mother's first suggestion of "Looney").

The first film he's now remembered for after signing with MGM in 1933 is Manhattan Melodrama, the film John Dillinger had just seen at Chicago's Biograph cinema before he was shot down by the FBI. He plays Clark Cable, the film's gangster hero, as a child. The first classic movie in which he has a memorable role was a loan-out to Warner Brothers in 1935, playing Puck in Max Reinhardt's all-star A Midsummer Night's Dream. Within a couple of years, he had become one of the two greatest child stars in the great decade of such performers (the other was Fox's Shirley Temple), with three prongs to his career. The first was a succession of serious roles, most significantly as the cabin boy in Victor Fleming's Captains Courageous and the cocky juvenile delinquent at reform school in Boys Town, playing opposite Spencer Tracy in both. The second was the series of small-town family comedies, 14 of them in all, cast as Andy Hardy, the jackanapes son of a small-town judge. The third prong was the partnership with MGM's recent signing, Judy Garland, that began with the racetrack story Thoroughbreds Don't Cry (1937) and continued for a dozen years.

Rooney was a fireball of confident, life-enhancing energy, endlessly active, cheerful and optimistic, an antidote to the depression yet realistic, appealing and warm in a way his frequent co-star, the stuck-up British child actor Freddie Bartholomew, wasn't. "He's the perfect composite of everyone's kid brother," wrote Frank S Nugent, the New York Times film critic who was later to become a leading screenwriter. But never growing taller than 5ft2in, Mickey was to remain a juvenile performer well into his 20s, despite the first of what were eventually to be eight marriages (the first Mrs Rooney was the unknown starlet Ava Gardner) and a stretch in the army. He was only slightly exaggerating when he later remarked: "I was a 14-year-old boy for 30 years."

In 1938, he received a special juvenile Oscar and the following year and for two further years was voted the biggest box-office attraction in America and Britain. In 1944, as the former jockey with a drinking problem, he played opposite Elizabeth Taylor in National Velvet, the film that made her a star. This proved, however, to be a triumphant end to the spectacular first stage of his career, and he was never again to experience such unbroken success or comparable adulation. He returned from military service in 1947 to make a series of failures, not all of them bad (Summer Holiday, Rouben Mamoulian's musical version of Eugene O'Neill's Ah, Wilderness! is now something of a cult classic), and he acrimoniously ended his MGM contract to go freelance.

He was in constant employment, with major roles in minor movies, minor ones in superior productions, rarely if ever playing a mature figure with an everyday job, family or social responsibilities. His characters were misfits with chips on their shoulder, eccentrics and outsiders. They were people on the margins of conventional society, among them angry standup comics, gangsters, boxers, jockeys, racing drivers, hyperactive career soldiers, sailors and airmen. They reflected his difficult life and discontented, unaccommodating personality and his problems with drugs, drink and personal finance (this last due to alimony and unwise investments).

His finest performance was almost certainly the title role in Don Siegel's ultra-low-budget, rarely revived gangster classic Baby Face Nelson (1957). His most memorably bad role is unarguably Holly Golightly's angry Japanese neighbour in Blake Edwards's Breakfast at Tiffany's (1961). He was outstanding as the dedicated second to fading boxer Anthony Quinn in Ralph Nelson's Requiem for a Heavyweight (1962) in an ensemble that included Jackie Gleason (as Quinn's manager) and Julie Harris. He made a highly amusing contribution to Pulp (1972), the film that Mike Hodges and Michael Caine thought would be an acclaimed encore after Get Carter (sadly, it wasn't). But seven years later, in the lyrical The Black Stallion, he received an Oscar nomination as best supporting actor.

Along the way there was a lot of work in broadcasting, much of it highly lucrative, some of it much acclaimed and leading to nominations and an Emmy award. The important, impressive thing is that he carried on working. There was serious trouble in 1966 over his fifth marriage when his wife's lover shot her and then killed himself using Mickey's gun. Like a great trouper, he rolled with the punches, kept on going and experienced a religious conversion. I only saw him once on stage, packing the Savoy in London in Sugar Babies in the late 1980s, co-starring with Anne Miller, another great survivor. His breathing was terrible, the old-time vaudeville sketches awful, his dancing frenetic. But his personal energy and the historic aura he brought on stage with him captivated us for the whole evening. In his last film to date, Shawn Levy's highly popular Night at the Museum (2006), he co-starred with veteran Dick Van Dyke and the film's real crowd-puller Ben Stiller as night attendant at a New York ethnographical museum. He didn't have much to do, but it was a rare treat to see the 86-year-old Rooney on the screen as belligerent as ever.

Rooney on marriage "Always get married in the morning. That way if it doesn't work out you haven't wasted a whole day."

Don Siegel on Rooney "Mickey ins one of the most talented actors I've ever worked with. However, the combination of Mickey and a six-pack was usually a disaster. He'd become vicious, morose and very stubborn. I liked him. He was a superb athlete. But with a beer can in his hand and 12 swirling around in his stomach, he became a perfect parody of Baby Face Nelson. If one could hold down that wonderful energy that he would burst out with, he had no peer… To give the devil (and he was one) his due, I admired his skill and loathed his personality."

Religion In the early 1970s, he became a proselytising born-again Christian, and his son, Mickey Rooney Jr, is a born-again minister in California.